Holiday How-to: Chocolate Leaves

My mom was a chemistry and home-ec teacher, so I grew up in a home where ingredients were carefully measured and food items were attractively arranged. While I got to help out in the kitchen as much as I wanted, I always liked being in the kitchen around the holidays. There were always new tricks or special touches added to dishes and along with these came short science lessons on why we were doing things that particular way.

One of my favorite things to help with in the kitchen were chocolate leaves. When done correctly, these are perfect little molds of the living leaf, just like the perfect molds and casts in the Morian Hall of Paleontology.

A chocolate leaf is made by smearing melted chocolate onto a leaf and putting it into the fridge to harden. Sounds easy, right? It is pretty easy. Read on!


Activity: Chocolate Leaves


Leaves (*See note in step 1.)

Chocolate candy melts

Parchment or wax paper

A cookie sheet or plate for your leaves to rest on as they cool


1. Pick your leaves. I like to use slightly waxy leaves so you don’t have to worry about fuzzy bits in your chocolate. NOTE: Learn about the plant you are picking leaves from before you decide to use them. Many household plants are decorative but poisonous.  Oleander is a great example of a plant that is pretty but poisonous. If you hate botany or don’t know about the Internet, getting pre-packaged basil or mint from the grocery store is a safe way to go. These leaves will be a little less firm, so you will need to be more careful with them.

2. Don’t pick leaves from poisonous plants. Seriously.

3. Wash your leaves with soap and water, rinse them thoroughly and then dry them completely. The chocolate won’t stick to wet leaves, so don’t rush this step. You will only be frustrated.

4. Put wax or parchment paper on a cookie sheet or plate. You want this to be something that will fit in the fridge with no problems.

5. Get out your candy melts. The melts come in a hundred colors. We are using chocolate colored ones in this tutorial. There will be instructions on the package on how to melt the specific brand of melts you purchased. In general, you will put the melts in a microwave safe bowl and microwave them a few seconds at a time stirring as you go. Don’t overheat the melts. They get gross and there is no coming back from that.

6. When you have everything melted and creamy, hold the leaf by its stem. I like pinching it between my thumb and index finger and then using my middle and ring finger to support the leaf. Do what feels comfortable to you.

7. Dip your stirring spoon into the chocolate. Use the BACK of the spoon to spread the chocolate on the leaf. Make sure the chocolate is thick enough that it won’t break when you try to peel it. Place the leaves on the parchment as you work, and don’t let them touch.


8. The side of the leaf you use is up to you. If you are using mint and you put the chocolate on the back of the leaf, you will have some crazy patterns.  If you want something more subtle, use the front of the leaf. Coat the leaf almost to the edges. If you go too far, you will get ugly edges that are hard to peel. But don’t worry! Those leaves are the best to eat.

9. Put the tray of leaves in the fridge and wait a few minutes.


10. When the chocolate is set, peel the leave off the chocolate. You should have a perfect little mold of your original leaf. This may take a little practice. Work quickly as you have something designed to melt with heat in your hot little hands.

11. Done! You can store the leaves in the fridge until you are ready to use them. If the leaves got soft when you were working with them, put them back in the fridge to firm them up. Once they are firm, you can toss them in a plastic container.


Okay! So what’s the science here?

The word “chocolate” comes from the Nahuatl word Xocolatl for “bitter water,” referring to its original incarnation as a hot, spiced beverage in the Mayan and Aztec traditions. Traditionally, chocolate is a mixture of cacao powder, cocoa butter, and a sweetener. To make chocolate palatable and stable, we now mix milk solids, added flavors, modifiers, and preservatives.

Those candy melts? NOT CHOCOLATE! In this example, they are sort of chocolate colored, so they have that going for them, but they also come in a bunch of colors that are not known to nature so… not chocolate. They are mostly made of sugar and vegetable fats – not cocoa butter – and depending on the brand, they may throw in a little wax for better melting. Mmmmm… wax.

The advantage to the melts over the regular chocolate is that they do have the wax and the vegetable oil in them, which makes melting easier since the chocolate doesn’t need to be tempered. It hardens pretty quickly and sticks to whatever you dip in it, so it makes a great coating for cake pops or whatever crazy things show up on Pinterest this month.

Want to get super nerdy about your chocolate?  (I assume you do…) MIT has these tidbits available.

What’s in typical chocolate?

  • 10-20% cacao
  • 8-16% milk solids
  • 32-60% sugar
  • 10-20% cocoa butter
  • 2% theobromine and polyphenols

Cocoa Butter Chemistry

Fats and oils are organic molecules made up of three fatty acids chemically linked by an ester bond to glycerol. Fats are solid at room temperature, while oils are liquid.

Cocoa butter fats are made up predominantly by three major fatty acid molecules: Palmitic Acid, Stearic acid, and Oleic acid.

Oleic acid is unsaturated (has a double bond on its carbon chain), making it kinked and unable to pack well with other molecules. Because of this, a greater portion of oleic acid in the fat results in a lower melting temperature for the cocoa butter.

Chocolate makers can adjust the amounts of each fatty acid to produce a chocolate that melts only in the mouth, giving it a superior quality.

Tempering chocolate

The cocoa butter in chocolate can have several different crystal structures (three-dimensional patterns in which the fat molecules pack). There are six known chocolate crystal forms, or polymorphs. You can obtain each form by varying the fatty acid ratios and the temperature at which the chocolate is tempered (cooled).

Only a few of the polymorphs are considered good for gourmet chocolate because they give the right blend of snap (when you bite into the chocolate) and melting (when it warms up in your mouth). Melting is especially important because it controls how well the chocolate disperses and releases flavor onto your tongue.

Whether you will be constructing culinary masterpieces this fall or sitting back and enjoying the kitchen creations of others, we hope you have a happy holiday with you and yours!  (And when you’ve had a little too much togetherness, we will be open on Friday…)

What’s ancient, allegedly apocalyptic and opening Friday? The Maya 2012 exhibit, that’s what!

Maya 2012Forget about the world ending and all those rumors about Dec. 21, 2012. The question of the moment is: What will happen on Oct. 26, 2012?

If you guessed that our Maya 2012: Prophecy Becomes History exhibit opens, you’d be correct. See for yourself why the Maya civilization was successful for over three millennia … and find out when (and whether) the world’s actually going to end on that infamous day in December.

Tickets to Maya 2012 also include admission to another new exhibit opening this Friday, Gems of the Medici. So now that we’ve made you a deal you can’t refuse, don’t. Buy your tickets and find out whether we’ll all make it to 2013.

What do you know about 2012? [Quiz]

To celebrate our new Planetarium Show 2012: Mayan Prophecies, we are testing your knowledge of the significant Maya date of December 21, 2012. How much do you know about this important day?

Are these statements TRUE or FALSE?

1. Dec. 21, 2012 marks the end of the longest Mayan time cycle.

2. The Aztecs knew about 2012.

3. In 2012, solar storms will burn the surface of the Earth.

4. Dec 21, 2012 is a significant celestial date.

5. The Maya used the 26,000-year precession cycle to predict events in 2012.

6. There will be a cataclysmic event in 2012.

7. An impending pole shift will tear the Earth apart in 2012.

8. There is a special alignment of the sun in front of the Milky Way galaxy on Dec. 21, 2012.

9. A rogue planet, such as Nibiru or Eris or Planet X, is going to destroy the Earth in 2012.

10. A geomagnetic reversal in 2012 will devastate the planet.

11. A “global awakening” is coming in 2012, leading to a societal transformation.

12. The Earth will pass through the Galactic plane.

2012: Mayan Prophecies
A scene from 2012: Mayan Prophecies, Now Showing in the HMNS Planetarium!


1. Dec. 21, 2012 marks the end of the longest Mayan time cycle.
TRUE: Dec. 21, 2012 is the beginning of the 13th Baktun in the Maya Long Count. This is a day of celebration, much like Jan. 1, 2000 was for us.

2. The Aztecs knew about 2012.
FALSE: There is no archeological evidence that 2012 was significant to any other MesoAmerican civilization.

3. In 2012, solar storms will burn the surface of the Earth.
FALSE: A massive solar storm could take out a satellite, but cannot reach Earth’s surface. Also sunspot maximum will occur in 2013.

4. Dec 21, 2012 is a significant celestial date.
TRUE: Every year, December 21 is the winter solstice when the sun makes its lowest trip across the sky in the Northern Hemisphere.

5. The Maya used the 26,000-year precession cycle to predict events in 2012.
FALSE: The Maya may have observed slow changes in the sky due to precession, but this cycle was never recorded.

6. There will be a cataclysmic event in 2012.
TRUE: There will be volcanic eruptions, floods, earthquakes, tornadoes, and hurricanes in 2012 – just like every year on our dynamic planet.

7. An impending pole shift will tear the Earth apart in 2012.
FALSE: The poles wander at a speed of about 1 degree per million years.

8. There is a special alignment of the sun in front of the Milky Way galaxy on Dec. 21, 2012.
TRUE: On the winter solstice, the sun is now in front of a dark rift in the Milky Way band, close to the direction of the Galaxy’s center as it has been for several years.

9. A rogue planet, such as Nibiru or Eris or Planet X, is going to destroy the Earth in 2012.
FALSE: Eris is now beyond Pluto. There is no Planet X. The Babylonian Nibiru was probably Jupiter. The Maya only knew Mercury, Venus, Mars, Jupiter, and Saturn.

10. A geomagnetic reversal in 2012 will devastate the planet in 2012.
FALSE: Geomagnetic reversals do happen and we may be overdue for one. These take thousands of years to occur and are not destructive.

11. A “global awakening” is coming in 2012, leading to a societal transformation.
TRUE: Well, 2012 is a presidential election year for the United States and for Mexico and the diamond jubilee of the Queen.

12. The Earth will pass through the Galactic plane.
TRUE: The Earth will cross the Galactic Equator, but in about 27 million years.

Come learn more about Maya culture and their calendar in our new Planetarium show, 2012: Mayan Prophecies, open now.

2012: Did the Maya Predict an Apocalypse?

For the last 2 years, the Astronomy Department of the Houston Museum of Natural Science has searched and researched Maya ruins and writings for connections between the Mayan calendar and the ability of Maya astronomers to predict future events.

To record the passage of time, the Maya developed a 260-day ritual cycle, made up of thirteen numbers and twenty names. With this continuous running cycle, they could predict future events like the harvesting of crops and the birth of children. The Maya kept a second 365-day solar calendar of 18 months, each lasting 20 days, plus 5 extra days to complete the year. This calendar determined the growing season and the annual return of the rains. For longer time periods the Maya used a 5-number Long Count. On December 21st, 2012, for instance, this Long Count has a new beginning as the date changes from to This is similar to the change from 1999 to 2000 in our modern calendar and is the cause of much 2012 speculation.

Great Temples
The homeland of the Maya stretches from southern Mexico to northern Central America. Our new planetarium show, 2012: Mayan Prophecies (Now Showing!), explores the great Maya cities of Uxmal, Chichen Itza, Tikal, and Palenque. For survival, the Maya created these great urban centers to store rainwater through the dry season and built observatories to determine when the annual rains would begin.

The Castillo pyramid in Chichen Itza is a temple to the feathered serpent god Kukulcan. Each of its 4 staircases has 91 steps for 364 steps in all with a top step into the temple – one step for each day of the year.  According to legend, Kukulcan returns to his pyramid on the vernal and autumnal equinoxes, descending the staircase in an undulating shadow.

In the nearby Caracol observatory, astronomers watched Kukulcan, who appeared in the heavens as the planet Venus. Through motions of the brilliant Venus, they determined the will of Kukulcan and the time for human sacrifices to honor this sky god and give thanks for the rains he would soon send.

photo courtesy of Raymond Ostertag

The Maya carved the great city of Tikal out of the rain forest in the lowlands of modern Guatemala. In this city of up to 100,000, all water came from the sky. Tikal’s rulers cleared the rain forest, channeled the water in swamps to grow crops, and built cisterns and catch basins to store water during the rainy season. Tikal’s power depended on storing enough water to last until the rains returned each spring.

Five giant pyramids helped astronomers predict when the rainy season would begin. On December 21, for instance, astronomers on Temple 4 could watch the sun rise farthest to the south, over the Pyramid of the Jaguar Priest. From this date forward, they knew that the sun would rise a little more to the north each day. At the vernal equinox, the sun would always rise over Temple 1, an event that must happen before the rains could begin.

In the foothills of Mexico’s southern mountains, lies the Maya city of Palenque. Blessed with abundant rain and flowing rivers, the artisans of Palenque had time to create some of the most elaborate and exquisite Mayan art and the most delicate of buildings. Here inscriptions describe the beginning of the Maya long count cycle and chronicle events far into the future, but no mention of 2012.

There has been a subtle change in the sky in the 1,300 years since the time of the classic Maya. Due to the wobble of Earth’s spin axis, different stars rise with the sun in each season.

For instance, at the time of the Maya, the glowing Milky Way band was above the sun at sunrise on the winter solstice.  Now in December, the sun reaches its lowest point at noon in front of a dark rift in the Milky Way, near the direction of the galaxy’s center.

Does this mean that galactic forces are now aligned? Did the Maya predict this alignment? We have no data to indicate that the Maya recognized the 26,000-year cycle that caused this alignment. There is no documented connection between the Earth-centered Maya cosmos and our modern universe.

Classic Maya civilization did experience a great apocalypse, but it occurred long before the Spanish Conquest.

For over a millennium, the major cities of the Maya have stood abandoned – deserted by their citizens, conquered by weather and reclaimed by the rainforest. At their culture’s height, many of the Maya faced the worst drought in thousands of years. It devastated a civilization that had cut down the rainforest to grow crops and destroyed urban centers that could not store enough water for their people. In less than a hundred years, over a hundred thousand Maya disappeared, leaving their parched cities and their withered fields, rejecting the divine right and Earthly power of their kings. By the thousands they returned to the rainforest and mountains to a sustainable population and way of life.

As we sense the fragility of our own culture today, we may discover a warning for 2012 in the ruins of these great Maya cities — silent sentinels, witnesses of the apocalypse of the Maya.

Explore pyramids towering above the rainforest, designed as observatories to follow the sun. Experience the apocalypse of the Maya and discover how our fate in 2012 may be foretold in our new planetarium show 2012: Mayan Prophecies. Check out the extended preview below!

Can’t see the video? 2012: Mayan Prophecies from HMNS on Vimeo.